Supplementary Figure 1: Assessment of data variability, quality and summary of PDT database.

(a) Comparison of kinase inhibitor selectivity as determined by a Discover-X assay (this study) and Klaeger et al. (Science 358, 2017) for compounds present in both datasets. (b) Coefficients of variation of phosphopeptide peak areas in basal (DMSO controls) samples as a function of peak area cut-off values (n = 4 independent experiments). (c) Number of phosphopeptides quantified as a function of peak area intensity cut-off values. (d) Number of phosphorylation sites with CV<50% in basal (untreated) cells. (e) Number of unique phosphorylation sites found to be putative downstream targets (PDTs) of at least one kinase. (f) Number of kinases with at least five PDTs.